CN111909004A - Method for separating m-cresol from p-cresol - Google Patents
Method for separating m-cresol from p-cresol Download PDFInfo
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- CN111909004A CN111909004A CN201910389208.XA CN201910389208A CN111909004A CN 111909004 A CN111909004 A CN 111909004A CN 201910389208 A CN201910389208 A CN 201910389208A CN 111909004 A CN111909004 A CN 111909004A
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- IWDCLRJOBJJRNH-UHFFFAOYSA-N p-cresol Chemical compound CC1=CC=C(O)C=C1 IWDCLRJOBJJRNH-UHFFFAOYSA-N 0.000 title claims abstract description 185
- RLSSMJSEOOYNOY-UHFFFAOYSA-N m-cresol Chemical compound CC1=CC=CC(O)=C1 RLSSMJSEOOYNOY-UHFFFAOYSA-N 0.000 title claims abstract description 170
- 238000000034 method Methods 0.000 title claims abstract description 46
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 60
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims abstract description 31
- 238000000926 separation method Methods 0.000 claims abstract description 30
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 20
- 239000008139 complexing agent Substances 0.000 claims abstract description 17
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000004202 carbamide Substances 0.000 claims abstract description 16
- 230000000536 complexating effect Effects 0.000 claims abstract description 14
- 239000000203 mixture Substances 0.000 claims abstract description 10
- 238000002425 crystallisation Methods 0.000 claims abstract description 6
- 230000008025 crystallization Effects 0.000 claims abstract description 6
- 239000000126 substance Substances 0.000 claims abstract description 5
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 198
- 239000007788 liquid Substances 0.000 claims description 42
- 238000010438 heat treatment Methods 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 18
- 239000000047 product Substances 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 12
- 239000012065 filter cake Substances 0.000 claims description 12
- 238000004064 recycling Methods 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
- 238000000967 suction filtration Methods 0.000 claims description 7
- 239000012153 distilled water Substances 0.000 claims description 6
- 230000003301 hydrolyzing effect Effects 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000005303 weighing Methods 0.000 claims description 5
- 238000001914 filtration Methods 0.000 claims description 4
- 239000002994 raw material Substances 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 238000007670 refining Methods 0.000 abstract description 3
- 239000003245 coal Substances 0.000 abstract description 2
- 230000009286 beneficial effect Effects 0.000 abstract 1
- 238000013386 optimize process Methods 0.000 abstract 1
- 230000035484 reaction time Effects 0.000 abstract 1
- 239000012071 phase Substances 0.000 description 18
- NXXYKOUNUYWIHA-UHFFFAOYSA-N 2,6-Dimethylphenol Chemical compound CC1=CC=CC(C)=C1O NXXYKOUNUYWIHA-UHFFFAOYSA-N 0.000 description 10
- IXQGCWUGDFDQMF-UHFFFAOYSA-N 2-Ethylphenol Chemical compound CCC1=CC=CC=C1O IXQGCWUGDFDQMF-UHFFFAOYSA-N 0.000 description 9
- VQTUBCCKSQIDNK-UHFFFAOYSA-N Isobutene Chemical compound CC(C)=C VQTUBCCKSQIDNK-UHFFFAOYSA-N 0.000 description 5
- 238000005804 alkylation reaction Methods 0.000 description 5
- 238000000746 purification Methods 0.000 description 5
- 230000029936 alkylation Effects 0.000 description 3
- 238000010668 complexation reaction Methods 0.000 description 3
- 229930003836 cresol Natural products 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 3
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 description 2
- 239000002168 alkylating agent Substances 0.000 description 2
- 229940100198 alkylating agent Drugs 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- -1 -tert-butyl cresol Chemical compound 0.000 description 1
- 239000011831 acidic ionic liquid Substances 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 150000001896 cresols Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 125000000552 p-cresyl group Chemical group [H]C1=C([H])C(=C([H])C([H])=C1O*)C([H])([H])[H] 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000005292 vacuum distillation Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/685—Processes comprising at least two steps in series
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
- C07C37/84—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by crystallisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/86—Purification; separation; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a method for separating m-cresol and p-cresol, and relates to the field of fine separation in the technical field of coal chemical industry. The method for separating m-cresol and p-cresol disclosed by the invention comprises the following steps: m-cresol and p-cresol with purity of more than 98% are obtained by taking m-cresol and p-cresol obtained by vacuum rectification of crude phenol as raw materials, adopting common urea and oxalic acid as complexing agents, performing two-step complexing crystallization, and controlling temperature and reaction time in the complexing and crystallization processes. The beneficial effects are as follows: the method aims at the composition characteristics of m-cresol and p-cresol to obtain the optimized process and parameters for refining and separating phenol products; the whole process flow is simple, the product quality is high, the production cost is low, and the method is an economical and feasible m-cresol and p-cresol fine separation process.
Description
Technical Field
The disclosure relates to the field of fine separation in the technical field of coal chemical industry, in particular to a method for separating m-cresol and p-cresol.
Background
M-cresol and p-cresol are relatively common coal tar crude phenol vacuum distillation extracts, and because m-cresol and p-cresol have similar boiling points, m-cresol and p-cresol cannot be separated through conventional distillation, and generally appear as mixed components, so that the additional value is relatively low. In order to increase the added value, further separation must be carried out to obtain a pure product.
At present, the conventional methods for separating cresol isomers include a crystallization separation method, a complex addition method, an alkylation separation method and a molecular sieve adsorption method. For example, patent No. CN107721827A discloses a method for refining m-cresol and p-cresol, which comprises introducing crude m-cresol and p-cresol into a light component removing tower, rectifying the crude m-cresol to obtain high purity 2, 6-xylenol, introducing into a heavy component removing tower, and rectifying to obtain high purity o-ethylphenol and m-cresol; the patent with the application number of CN106831355A discloses a mixed m-p-cresol high-pressure fixed bed alkylation method, which comprises the steps of pressurizing and liquefying an alkylating agent, injecting the liquefied alkylating agent and mixed phenol into a reactor, keeping the pressure of the fixed bed reactor at 1.7-4.2 MPa and the temperature at 50-110 ℃, and reacting at the airspeed of 0.1-5 h < -1 > to obtain a self-polymerization product of isobutene, a mono-tert-butyl product of m-p-cresol and a di-tert-butyl product of m-p-cresol; the patent with application number CN104098445B discloses a method for extracting m-cresol from a m-cresol and p-cresol mixture, wherein the m-cresol and p-cresol mixture is combined with urea into a solid, the obtained solid is washed by using a mixed solvent, water is added into the washed solid for hydrolysis, an oil phase is separated, and the oil phase is subjected to reduced pressure distillation to obtain the m-cresol. The patent with application number CN106810422A discloses a method for separating m-cresol and p-cresol by liquid phase alkylation, which utilizes a new process that isobutylene mixed gas and a mixture of m-cresol and p-cresol are simultaneously subjected to alkylation reaction and separation in a fixed bed reactor under a liquid phase state to obtain m-cresol and p-cresol. The patent with application number CN104496759A discloses a separation method of m-cresol and p-cresol mixture, which takes m-cresol and p-cresol mixture liquid and isobutene gas as raw materials, uses an immobilized acidic ionic liquid as a catalyst to perform alkylation reaction in a fixed bed, and performs tert-butyl removal on the obtained mono-tert-butyl cresol, thereby obtaining high-purity m-cresol and p-cresol.
In the above method, there are problems such as large equipment investment, high energy consumption, and corrosion of equipment.
Disclosure of Invention
The purpose of the disclosure is to overcome the defects of the prior art and provide a method for separating m-cresol and p-cresol, which has the advantages of low equipment investment, low energy consumption, low equipment corrosion and simple process flow.
The technical scheme of the method for separating m-cresol and p-cresol provided by the disclosure is as follows:
the method comprises the following steps:
(1) separation of m-cresol:
weighing a certain amount of mixed phenol of m-cresol and p-cresol, putting the mixed phenol into a reactor, taking m-cresol as a reference, firstly adding a proper amount of complexing agent urea, stirring, heating to 50-90 ℃, stopping heating, carrying out complexing reaction, starting to dropwise add toluene into the reactor when the feed liquid is naturally cooled to 35-45 ℃, continuously reducing the temperature of the feed liquid, stopping dropwise adding toluene when the temperature is cooled to-15-5 ℃, and cooling and crystallizing; then filtering and washing the filter cake with toluene; finally, dissolving the filter cake with distilled water, separating the solution to obtain an upper oil phase, and distilling the oil phase to obtain m-cresol;
(2) separation of p-cresol:
after separating m-cresol, the residual phenol liquid is mainly p-cresol, taking p-cresol as a reference, firstly adding a proper amount of oxalic acid, stirring, heating to 80-110 ℃, carrying out a complexing reaction for a certain time, beginning to dropwise add toluene, continuously reducing the temperature of the feed liquid, and stopping dropwise adding toluene when the temperature of the feed liquid is statically cooled to-5-10 ℃; then, carrying out suction filtration to obtain a white solid; finally, hydrolyzing the white solid by using hot water at the temperature of 30-40 ℃, separating the liquid, evaporating toluene and water from the upper oil phase at normal pressure, and carrying out vacuum rectification under a vacuum condition to cut fractions to obtain a p-cresol product;
(3) and (3) recycling the solvent:
and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
The method comprises the steps of separating and extracting m-cresol in m-cresol and p-cresol by using urea as a complexing agent, separating and extracting p-cresol in phenol liquid after cresol is extracted by using oxalic acid as a complexing agent, and separating the m-cresol and the p-cresol by the two-step separation; the whole process flow is reasonable, the product quality is high, the production cost is low, and the method is an economical and feasible m-cresol and p-cresol fine separation process.
In the step (1), the ratio of the amount of the complexing agent urea to the amount of the m-cresol is 0.8-1.4.
Wherein, in the step (1), after stirring and heating to 70-80 ℃, the heating is stopped, and the complex reaction is carried out.
Wherein, in the step (1), when the temperature is cooled to-15 to-10 ℃, the dropping of toluene is stopped, and cooling crystallization is carried out.
In the step (1), the volume of the toluene dripped into the reactor is 2-4 times of the volume of the mixed phenol of the m-cresol and the p-cresol.
Wherein in the step (2), the mass ratio of the oxalic acid to the p-cresol is 1-1.3.
Wherein, in the step (2), the complex reaction is carried out for a certain time after stirring and heating to 95-105 ℃.
Wherein, in the step (2), when the temperature of the feed liquid is statically cooled to 0-5 ℃, the dropwise addition of the toluene is stopped.
Wherein, in the step (2), the volume of the toluene added into the reactor in a dropwise manner is 2-4 times of the volume of the phenol liquid in the process of separating the p-cresol.
Detailed Description
The embodiments described in the following exemplary disclosure do not represent all embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.
The invention provides a method for separating m-cresol and p-cresol, which comprises the following steps:
(1) separation of m-cresol: weighing a certain amount of mixed phenol of m-cresol and p-cresol, putting the mixed phenol into a reactor, taking m-cresol as a reference, firstly adding a proper amount of complexing agent urea, stirring, heating to 50-90 ℃, stopping heating, carrying out complexing reaction, starting to dropwise add toluene into the reactor when the feed liquid is naturally cooled to 35-45 ℃, continuously reducing the temperature of the feed liquid, stopping dropwise adding toluene when the temperature of the feed liquid is cooled to-15-5 ℃, and cooling and crystallizing; then filtering and washing the filter cake with toluene; finally, dissolving the filter cake with distilled water, separating the solution to obtain an upper oil phase, and distilling the oil phase to obtain m-cresol;
(2) separation of p-cresol: after separating m-cresol, the residual phenol liquid is mainly p-cresol, taking p-cresol as a reference, firstly adding a proper amount of oxalic acid, stirring, heating to 80-110 ℃, carrying out a complexing reaction for a certain time, then starting to dropwise add toluene, continuously reducing the temperature of the feed liquid, and stopping dropwise adding toluene when the temperature of the feed liquid is statically cooled to-5-10 ℃; then, carrying out suction filtration to obtain a white solid; finally, hydrolyzing the white solid by using hot water at the temperature of 30-40 ℃, separating liquid to obtain an upper oil phase, distilling toluene and water out of the upper oil phase under normal pressure, and carrying out reduced pressure rectification under a vacuum condition to cut fractions to obtain a p-cresol product;
(3) and (3) recycling the solvent: and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
The method comprises the steps of separating and extracting m-cresol in m-cresol and p-cresol by using urea as a complexing agent, separating and extracting p-cresol in phenol liquid after cresol is extracted by using oxalic acid as a complexing agent, and separating the m-cresol and the p-cresol by the two-step separation; the whole process flow is reasonable, the product quality is high, the production cost is low, and the method is an economical and feasible m-cresol and p-cresol fine separation process.
Preferably, in step (1), the ratio of the amount of the substance of the complexing agent urea to the amount of the substance of m-cresol is 0.8 to 1.4.
Preferably, in the step (1), after stirring and heating to 70-80 ℃, the heating is stopped, and the complexing reaction is carried out.
Preferably, in the step (1), when the temperature is cooled to-15 to-10 ℃, the dropping of the toluene is stopped, and cooling crystallization is carried out.
Preferably, in the step (1), the volume of the toluene added dropwise to the reactor is 2 to 4 times of the volume of the mixed phenol of m-cresol and p-cresol.
Preferably, in the step (2), the mass ratio of oxalic acid to p-cresol is 1-1.3.
Preferably, in the step (2), after stirring and heating to 95-105 ℃, a complexing reaction is carried out for a certain time.
Preferably, in the step (2), when the temperature of the feed liquid is statically cooled to 0-5 ℃, the dropwise addition of the toluene is stopped.
Preferably, in the step (2), the volume of toluene added dropwise to the reactor during the separation of p-cresol is 2 to 4 times the volume of the phenol liquid.
The method for separating m-p-cresol according to the present invention will be described in detail by way of specific examples.
Example 1:
(1) separation and purification of m-cresol: weighing 200g of mixed phenol raw material, putting the mixed phenol raw material into a reactor, adding 84g of complexing agent urea according to the mass ratio of the complexing agent urea to the m-cresol of 1.2:1 in the mixed phenol raw material, stirring, heating to 80 ℃, stopping heating, carrying out complexing reaction, starting to dropwise add toluene when the temperature of the feed liquid is naturally cooled to 40 ℃, continuously reducing the temperature of the feed liquid, stopping dropwise adding toluene when the dropwise adding amount of the toluene is 600mL and the temperature of the feed liquid is cooled to-15 ℃, and cooling and crystallizing; then filtering, washing the filter cake with toluene, finally dissolving the filter cake with distilled water, separating liquid to obtain an upper oil phase, and distilling the upper oil phase to obtain 97.3g of m-cresol product with the content of 98.7 percent;
(2) separation and purification of p-cresol: after the separation of m-cresol, the residual phenol liquid contains 76.6% of p-cresol and 23.4% of m-cresol. The main component of the p-cresol is p-cresol, the p-cresol is separated by adopting an oxalic acid complexation method by taking the p-cresol as a reference, 68g of oxalic acid is added according to the mass ratio of the oxalic acid to the p-cresol of 1.2:1, the oxalic acid is stirred and heated to 100 ℃, the toluene is dripped after the reaction is carried out for 2.5 hours, the temperature of the feed liquid is continuously reduced, when the dripping amount of the toluene is 350mL, the temperature of the feed liquid is statically cooled to 5 ℃, the dripping of the toluene is stopped, and the cooling process needs about 15 hours; and then carrying out suction filtration to obtain a white solid, finally hydrolyzing with hot water at 30-40 ℃, distilling the oil phase after liquid separation out toluene and water at normal pressure, and then carrying out reduced pressure cutting under a vacuum condition to obtain a fraction, wherein 72.5g of a p-cresol product is obtained, and the content of the p-cresol product reaches 99.0%.
(3) And (3) recycling the solvent: and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
Example 2:
(1) separation and purification of m-cresol: weighing 200g of mixed phenol raw material, putting the mixed phenol raw material into a reactor, wherein m-cresol accounts for 50.9%, p-cresol accounts for 34.1%, 2, 6-xylenol accounts for 6.1%, and 2-ethylphenol accounts for 8.9%, taking m-cresol as a reference, adding 72g of complexing agent urea according to the mass ratio of the complexing agent urea to the m-cresol of 1.2:1, stirring, heating to 80 ℃, stopping heating, performing a complexing reaction, starting to dropwise add toluene when the temperature of the feed liquid is naturally cooled to 40 ℃, continuously reducing the temperature of the feed liquid, stopping dropwise adding toluene when the dropwise adding amount of the toluene is 500mL, and cooling and crystallizing when the temperature of the feed liquid is reduced to-10 ℃; then, carrying out suction filtration, washing the filter cake with toluene, finally dissolving the filter cake with distilled water, separating the liquid to obtain an upper oil phase, and distilling the upper oil phase to obtain 81.7g of an m-cresol product with the content of 99.1 percent;
(2) separation and purification of p-cresol: after the separation of m-cresol, the remaining phenol liquid contains 57.7% of p-cresol, 17.0% of m-cresol, 15.0% of 2-ethylphenol and 10.3% of 2, 6-xylenol. The main component of the p-cresol is p-cresol, the p-cresol is separated by adopting an oxalic acid complexation method by taking the p-cresol as a reference, 60g of oxalic acid is added according to the mass ratio of the oxalic acid to the p-cresol of 1.2:1, the oxalic acid is stirred and heated to 100 ℃, after 2 hours of reaction, the toluene is dripped, the temperature of the feed liquid is continuously reduced, when the dripping amount of the toluene is 300mL, the temperature of the feed liquid is statically cooled to 5 ℃, the dripping of the toluene is stopped, and the cooling process takes about 15 hours; and then carrying out suction filtration to obtain a white solid, finally hydrolyzing with hot water at 30-40 ℃, distilling the oil phase after liquid separation out toluene and water at normal pressure, and then carrying out reduced pressure cutting under a vacuum condition to obtain a fraction, wherein the content of the fraction is up to 99.0%, and the p-cresol product is 55.4 g.
(3) And (3) recycling the solvent: and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
Example 3:
(1) separation and purification of m-cresol: 300g of mixed phenol raw material is weighed and put into a reactor, wherein m-cresol accounts for 50.9 percent of the mixed phenol raw material, 34.1 percent of p-cresol, (50.9 percent of m-cresol, 34.1 percent of p-cresol, 6.1 percent of 2, 6-xylenol, 8.9 percent of 2-ethylphenol, based on m-cresol, 106g of complexing agent urea is added according to the mass ratio of the complexing agent urea to the m-cresol of 1.25:1, stirring, heating to 75 deg.C, stopping heating, performing complex reaction, adding dropwise toluene when the temperature of the material liquid is naturally cooled to 40 deg.C, continuously reducing the temperature of the material liquid, when the dosage of the toluene is 800mL, stopping dripping the toluene when the temperature of the feed liquid is cooled to-15 ℃, and cooling and crystallizing; then the mixture is filtered, and then the mixture is filtered, and washing the filter cake with toluene, finally dissolving the filter cake with distilled water, separating liquid to obtain an upper oil phase, and distilling the upper oil phase to obtain 130.8g of m-cresol product with the content of 99.2 percent.
(2) Separating and refining the p-cresol, and after separating the m-cresol, the residual phenol liquid comprises 60.4 percent of the p-cresol, 13.5 percent of the m-cresol, 15.5 percent of 2-ethylphenol and 10.6 percent of 2, 6-xylenol. The main component is p-cresol, the p-cresol is separated by adopting an oxalic acid complexation method, on the basis of the p-cresol, 110g of oxalic acid is added according to the mass ratio of the oxalic acid to the p-cresol of 1.3:1, the mixture is heated to 100 ℃, after 2.5 hours of reaction, the toluene is dripped, the temperature of the feed liquid is continuously reduced, when the dripping amount of the toluene is 500mL, the temperature of the feed liquid is statically cooled to 5 ℃, the dripping of the toluene is stopped, and the cooling process takes about 15 hours; and then carrying out suction filtration to obtain a white solid, finally hydrolyzing with hot water at 30-40 ℃, distilling the oil phase after liquid separation out toluene and water at normal pressure, and then carrying out reduced pressure cutting under a vacuum condition to obtain a fraction, wherein the content of the fraction is up to 99.1 percent, and the p-cresol product is 83.1 g.
(3) And (3) recycling the solvent: and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and disclosure be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.
Claims (9)
1. A process for separating m-cresol from p-cresol, characterized in that it comprises the following steps:
(1) separation of m-cresol:
weighing a certain amount of mixed phenol of m-cresol and p-cresol, putting the mixed phenol into a reactor, taking m-cresol as a reference, firstly adding a proper amount of complexing agent urea, stirring, heating to 50-90 ℃, stopping heating, carrying out complexing reaction, starting to dropwise add toluene into the reactor when the feed liquid is naturally cooled to 35-45 ℃, continuously reducing the temperature of the feed liquid, stopping dropwise adding toluene when the temperature of the feed liquid is cooled to-15-5 ℃, and cooling and crystallizing; then filtering and washing the filter cake with toluene; finally, dissolving the filter cake with distilled water, separating the solution to obtain an upper oil phase, and distilling the oil phase to obtain m-cresol;
(2) separation of p-cresol:
after separating m-cresol, the residual phenol liquid is mainly p-cresol, taking p-cresol as a reference, firstly adding a proper amount of oxalic acid, stirring, heating to 80-110 ℃, carrying out a complexing reaction for a certain time, then starting to dropwise add toluene, continuously reducing the temperature of the feed liquid, and stopping dropwise adding toluene when the temperature of the feed liquid is statically cooled to-5-10 ℃; then, carrying out suction filtration to obtain a white solid; finally, hydrolyzing the white solid by using hot water at the temperature of 30-40 ℃, separating liquid to obtain an upper oil phase, distilling toluene and water out of the upper oil phase under normal pressure, and carrying out reduced pressure rectification under a vacuum condition to cut fractions to obtain a p-cresol product;
(3) and (3) recycling the solvent:
and (3) separating the toluene evaporated in the steps (1) and (2), and distilling and purifying the toluene for recycling.
2. The method for separating m-cresol and p-cresol according to claim 1, wherein the ratio of the amount of the complexing agent urea to the amount of the substance of m-cresol in step (1) is 0.8 to 1.4.
3. The method for separating m-cresol and p-cresol according to claim 1 or 2, wherein in the step (1), after stirring and heating to 70 to 80 ℃, the heating is stopped and the complexing reaction is carried out.
4. The process for separating m-cresol or p-cresol according to claim 1 or 2, wherein in the step (1), when the temperature is cooled to-15 to-10 ℃, the addition of toluene is stopped, and cooling crystallization is carried out.
5. The method of separating m-cresol and p-cresol according to claim 1 or 2, wherein the volume of toluene added dropwise to the reactor in the step (1) is 2 to 4 times the volume of the mixed phenol of m-cresol and p-cresol.
6. The method for separating m-cresol and p-cresol according to claim 1, wherein the mass ratio of oxalic acid to p-cresol in step (2) is 1 to 1.3.
7. The method for separating m-cresol and p-cresol according to claim 1 or 6, wherein the complexing reaction is carried out for a certain period of time after the mixture is stirred and heated to 95-105 ℃.
8. The method for separating m-cresol and p-cresol according to claim 1 or 6, wherein in the step (2), when the temperature of the feed liquid is statically cooled to 0-5 ℃, the dropwise addition of toluene is stopped.
9. The process for separating m-and p-cresol according to claim 1 or 6, wherein in the step (2), the volume of toluene added dropwise to the reactor during the separation of p-cresol is 2 to 4 times the volume of the phenol liquid.
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